Handle MustScanSubDirs for large projects

When you scan a really large folder for file event changes, the client
or kernel might not be able to keep up with all the initial 'add' events
sent by fsevents.

This happens for me with our humongous vite project that has thousands
of files that are sent to firefox. At some point today, chokidar
receives undefined as file type when it's actually a rescan request, and
fsevents / chokidar attempts to unlink the directory instead of
rescanning it, making vite crash after a while instead of finishing
processing fsevents.

This might be a fix in the correct direction, but the maintainers here
are probably better at evaluating it. With this patch locally, vite no
longer stops working for large projects on initial load.

fsevents.js

@@ -50,6 +50,7 @@ function getInfo(path, flags) {
 function getFileType(flags) {
   if (events.ItemIsFile & flags) return "file";
   if (events.ItemIsDir & flags) return "directory";
+  if (events.MustScanSubDirs & flags) return "directory"; 
   if (events.ItemIsSymlink & flags) return "symlink";
 }
 function anyIsTrue(obj) {